Wells

an orbit is just falling and missing.

fling moons — find the speed that falls forever

A moon flung sideways never stops falling toward the planet; it only stops hitting it. Enough sideways speed curves that fall into a loop instead of a crash: no separate force holds an orbit up, just a fall at an angle that never lands.

Concepts: gravity, orbits.

An interactive you play with one thumb, on Wundr.